Quarantined messages are deleted after 30 days.

You can direct the Lineal Email Security Service to notify you by email when you have quarantined messages. When set to Yes, messages that would normally be blocked are instead quarantined. This setting does not apply to messages blocked by Sender or Content policies. On the Settings > Quarantine Notification page, select Scheduled. Click and drag in the Schedule notification intervals section to set the day and time for quarantine notification email delivery. Click to clear a selection. Alternatively, select Never if you do not want to receive quarantine notifications. Click  Save Changes  to save your settings.